1. Field of the Invention
The present invention relates generally to finite element analysis of a threaded fastener and, more specifically, to a system and method of generating a finite element mesh for a threaded fastener and joining structure assembly.
2. Description of the Related Art
Fastener design, and in particular the design of a threaded fastener, has advanced to a state in which computer-aided design techniques are frequently incorporated in the development and analysis of a threaded fastener and a structure joined together by the threaded fastener, such as two blocks. Computer-aided design is especially beneficial in analyzing a stress in a joining structure resulting from the load transfer through contacting threads of the threaded fastener and mating surfaces in the joining structure. For example, a fatigue failure, such as a crack in a thread root, may occur in a threaded portion of the joining structure. The ability to predict a stress and potential fatigue failure in a threaded fastener or joining structure under an operating load is advantageous in the design of the fastener and the bolted joint.
It is known to utilize a strain gauge to determine the state of stress on a part in which a load has been applied. However, it is extremely difficult to position a strain gage at the thread interface between the threaded fastener and the joining structure and still be able to recreate the stress. It is also difficult to reproduce the effect of other loading factors, including thermal loading.
It is also known to use a classical analytical technique to identify stresses and areas of high stress concentration within a structure. For example, the thread and joining structure behavior is approximated and the model is empirically corrected to fit experimental observations. However, this technique only evaluates stresses and fatigue in the bolt shank, bolt thread stripping, and bolt fatigue, and doesn't consider stress in the block threads or contacting surfaces.
Another known analytical technique is finite element analysis. In the past, a simple model was used to reduce model size and complexity. For example, the fastener and the joining structure are modeled in two dimensions, and a computer simulation is performed to approximate the stresses of the contacting threads. However, a two-dimensional analysis assumes that the bolt is axi-symmetric, and helical threads are not axi-symmetric. Thus, there is a need in the art for a system and method of generating a finite element mesh of a threaded fastener and a joining structure for stress analysis and evaluation purposes, to more accurately predict fatigue behavior.